forked from OSchip/llvm-project
196 lines
5.5 KiB
ReStructuredText
196 lines
5.5 KiB
ReStructuredText
llc - LLVM static compiler
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==========================
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SYNOPSIS
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--------
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:program:`llc` [*options*] [*filename*]
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DESCRIPTION
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-----------
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The :program:`llc` command compiles LLVM source inputs into assembly language
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for a specified architecture. The assembly language output can then be passed
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through a native assembler and linker to generate a native executable.
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The choice of architecture for the output assembly code is automatically
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determined from the input file, unless the :option:`-march` option is used to
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override the default.
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OPTIONS
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-------
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If ``filename`` is "``-``" or omitted, :program:`llc` reads from standard input.
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Otherwise, it will from ``filename``. Inputs can be in either the LLVM assembly
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language format (``.ll``) or the LLVM bitcode format (``.bc``).
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If the :option:`-o` option is omitted, then :program:`llc` will send its output
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to standard output if the input is from standard input. If the :option:`-o`
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option specifies "``-``", then the output will also be sent to standard output.
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If no :option:`-o` option is specified and an input file other than "``-``" is
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specified, then :program:`llc` creates the output filename by taking the input
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filename, removing any existing ``.bc`` extension, and adding a ``.s`` suffix.
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Other :program:`llc` options are described below.
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End-user Options
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~~~~~~~~~~~~~~~~
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.. option:: -help
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Print a summary of command line options.
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.. option:: -O=uint
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Generate code at different optimization levels. These correspond to the
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``-O0``, ``-O1``, ``-O2``, and ``-O3`` optimization levels used by
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:program:`llvm-gcc` and :program:`clang`.
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.. option:: -mtriple=<target triple>
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Override the target triple specified in the input file with the specified
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string.
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.. option:: -march=<arch>
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Specify the architecture for which to generate assembly, overriding the target
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encoded in the input file. See the output of ``llc -help`` for a list of
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valid architectures. By default this is inferred from the target triple or
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autodetected to the current architecture.
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.. option:: -mcpu=<cpuname>
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Specify a specific chip in the current architecture to generate code for.
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By default this is inferred from the target triple and autodetected to
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the current architecture. For a list of available CPUs, use:
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.. code-block:: none
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llvm-as < /dev/null | llc -march=xyz -mcpu=help
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.. option:: -filetype=<output file type>
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Specify what kind of output ``llc`` should generated. Options are: ``asm``
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for textual assembly ( ``'.s'``), ``obj`` for native object files (``'.o'``)
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and ``null`` for not emitting anything (for performance testing).
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Note that not all targets support all options.
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.. option:: -mattr=a1,+a2,-a3,...
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Override or control specific attributes of the target, such as whether SIMD
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operations are enabled or not. The default set of attributes is set by the
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current CPU. For a list of available attributes, use:
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.. code-block:: none
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llvm-as < /dev/null | llc -march=xyz -mattr=help
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.. option:: --disable-fp-elim
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Disable frame pointer elimination optimization.
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.. option:: --disable-excess-fp-precision
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Disable optimizations that may produce excess precision for floating point.
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Note that this option can dramatically slow down code on some systems
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(e.g. X86).
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.. option:: --enable-no-infs-fp-math
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Enable optimizations that assume no Inf values.
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.. option:: --enable-no-nans-fp-math
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Enable optimizations that assume no NAN values.
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.. option:: --enable-unsafe-fp-math
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Enable optimizations that make unsafe assumptions about IEEE math (e.g. that
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addition is associative) or may not work for all input ranges. These
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optimizations allow the code generator to make use of some instructions which
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would otherwise not be usable (such as ``fsin`` on X86).
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.. option:: --enable-correct-eh-support
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Instruct the **lowerinvoke** pass to insert code for correct exception
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handling support. This is expensive and is by default omitted for efficiency.
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.. option:: --stats
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Print statistics recorded by code-generation passes.
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.. option:: --time-passes
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Record the amount of time needed for each pass and print a report to standard
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error.
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.. option:: --load=<dso_path>
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Dynamically load ``dso_path`` (a path to a dynamically shared object) that
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implements an LLVM target. This will permit the target name to be used with
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the :option:`-march` option so that code can be generated for that target.
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Tuning/Configuration Options
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. option:: --print-machineinstrs
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Print generated machine code between compilation phases (useful for debugging).
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.. option:: --regalloc=<allocator>
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Specify the register allocator to use.
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Valid register allocators are:
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*basic*
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Basic register allocator.
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*fast*
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Fast register allocator. It is the default for unoptimized code.
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*greedy*
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Greedy register allocator. It is the default for optimized code.
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*pbqp*
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Register allocator based on 'Partitioned Boolean Quadratic Programming'.
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.. option:: --spiller=<spiller>
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Specify the spiller to use for register allocators that support it. Currently
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this option is used only by the linear scan register allocator. The default
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``spiller`` is *local*. Valid spillers are:
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*simple*
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Simple spiller
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*local*
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Local spiller
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Intel IA-32-specific Options
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.. option:: --x86-asm-syntax=[att|intel]
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Specify whether to emit assembly code in AT&T syntax (the default) or Intel
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syntax.
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EXIT STATUS
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-----------
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If :program:`llc` succeeds, it will exit with 0. Otherwise, if an error
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occurs, it will exit with a non-zero value.
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SEE ALSO
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--------
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lli
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